I've set up samba 3.0.1 on a two node tru64 manual failover cluster. I got the domain admin to create 3 machine accounts in the AD domain, one for each node and one for the cluster name (although not sure if all were necessary).
I joined both nodes to the domain using the net command.
I created a conf file for each node, and set the interfaces parameter to point to the IP of the cluster, and the netbios name to the cluster name. I then put all the shares in a separate conf which is called by the node confs. Finally I modified the samba start/shut script to check the pid of smbd and nmbd to avoid starting multiple instances.
The shares are accessible via the cluster name, e.g. \\frodo regardless of which node samba is running on.